1. Field of the Invention
The present invention relates to a system and method for controlling an internal combustion engine capable of performing auto-ignited combustion.
2. Description of Related Art
JP-A 10-196424 discloses a technique to control ignition time or timing of auto-ignited combustion of homogeneous air/fuel mixture charge. This technique requires elevating the temperature of mixture charge during compression stroke to accomplish temperature slightly below a threshold level at which the charge would be auto-ignited at around top dead center (TDC). In order to cause such auto-ignition at a desired ignition timing point, this technique employs means for providing an additional increase of cylinder pressure to further elevate the temperature to or beyond the threshold level.
Examples of such means are proposed in the above-mentioned published Japanese application. One such example is a device employing a control piston to reduce the volume of a combustion chamber. Another is a device employing a spark plug to ignite a portion of the charge to allow thermal expansion. This thermal expansion compresses the remaining or surrounding charge to induce auto-ignited combustion thereof.
These proposed devices, however, possess their own distinct disadvantages. The device employing a control piston is not sufficiently simple. On the other hand, the device employing a spark plug is not effective enough to increase a cylinder pressure to accomplish a sufficiently high level if the homogeneous air/fuel mixture charge is lean and has an air/fuel ratio greater than the stoichiometric air/fuel ratio.
The present invention aims at keeping such additional increase of cylinder pressure sufficiently high enough to induce auto-ignited combustion of lean air/fuel mixture without any complicated structure.
An object of the present invention is to provide a system and method for controlling an internal combustion engine such that, without any complicated structure, such additional increase of cylinder pressure is always kept sufficiently high enough to induce auto-ignited combustion of air/fuel mixture.
Another object of the present invention is to provide an internal combustion engine in which such additional increase of cylinder pressure is always kept sufficiently high enough to induce auto-ignited combustion of air/fuel mixture.
According to the present invention, there is provided a system for controlling an internal combustion engine capable of performing auto-ignited combustion, using a spark timing controller and a fuel supply controller, which have disparate control parameters, the system comprising:
at least one combustion chamber;
a spark plug arranged to produce, under control of the spark timing controller, a spark within the combustion chamber at a predetermined location;
a fuel supply device operable to perform, under control of the fuel supply controller, a first fuel injection, for each engine cycle, to create a first air/fuel mixture within the combustion chamber and a second fuel injection, in the same engine cycle, to localize fuel to create, in the neighborhood of the spark plug, a localized second air/fuel mixture portion, which is ignitable by the spark produced at the predetermined location;
a combustion event indicative (CEI) parameter generator for generating a CEI parameter related with one of combustion speed and ignition timing point of auto-ignition of auto-ignited combustion of the first air/fuel mixture, within the combustion chamber, which follows spark-ignited combustion of the second air/fuel mixture portion; and
a control parameter generator for determining at least one of the control parameters in response to CEI parameter and generating the determined control parameters.